Piston



Dec. 14, 1943. v s 2,336,918

PIsTdN' Filed Oct}. 31 1942 IN VEN TOR.

Patented Dec. 14, 1943 UNHTE STATES PATENT OFFICE 7 Claims.

This invention relates .to improvements in pistons.

The main objects of this invention are:

First, to provide a piston for internal combustion engines in which there is a large transfer of heat from the combustion surface of the piston to the ring belt section of the same and thence to the cooled cylinder walls, and also through the piston to the inner side of the same where the heat is carried off by the crank case oil and greases to thereby prevent overheating of said combustion surface and the consequent detonation of hydrocarbons over the piston and excessive use of lubricating oils.

Second, to provide a piston for internal combustion engines of a laminated structure in which the thermal conductivity of the metal adjacent the combustion chamber is relatively great compared to that of the metal beneath, and in which the bonding contact between the adjacent surfaces of said metals is of a serrated contour to insure against relative lateral displacement of said metals due to unequal degrees of expansion and contraction of same caused by changes in temperature.

Third, to provide a piston of a laminated structure of the character above described in which tivity towards the circumference of the piston and ring belt section with a consequent lowering of the temperature of the central portion of the combustion surface of the piston.

Objects relating to the details and economies of my invention will appear from the description to follow. The invention is pointed out in the claims.

A structure which embodies the features of my invention is clearly illustrated in the accompanying drawing in which:

Fig. l is a side view of the piston showing the lower portion in side elevation and the upper portion in central vertical section.

Fig. 2 is an enlarged detail fragmentary view showing in section and also in perspective a side and a head wall of a piston of the embodiment shown in Fig. l.

vFig. 3 is a fragmentary central vertical section of the heat portion of a modified form of my invention.

Fig. 4 is a fragmentary central vertical section of still another embodiment of the invention.

Referring to the accompanying drawing and more particularly to Figs. 1 and 2 showing one of the embodiments of the invention, reference numeral I designates the iron head wall or portion of a piston cast integrally with the iron skirt portion 2. To the top surface of the iron head wall I is secured in a manner hereinafter described, a layer 3 of copper. This layer of copper having thermal conducitivity relatively great compared to the iron head portion I and being of substantial thickness and covering substantially the entire top surface of the head portion I, said layer of copper facilitating rapid transfer of heat to the ring belt section 6- of the piston and thence to the cooled cylinder walls to thereby prevent overheating of the combustion surface of the piston and the consequent detonation of combustible gases by said overheated surface. In this embodiment as shown in Fig. 1, the layer 3 of copper does not extend completely across the top surface of the piston, but only to the central circular projecting iron portion or pilot 5 containing the lathe center 6 acquired for machining and preparing the top surface of the iron head I for the reception of the copper of layer 3. After the copper of layer 3 is united to the top surface of iron head portion l, as later described, this same pilot 5 with center 6 may be used in turning the piston ring grooves l and for finish grinding, with the required accuracy of engine builders. To keep the temperature low for the central projecting portion 5 the same is made as small as practical for machine operations, a three-eighths inch diameter being found very satisfactory. In the modification of the invention shown in Fig. 4 there is also the central projecting portion 5 on the head wall I, but in the modification of Fig. 3 this central iron projecting portion 5 is omitted from the head wall 9", the construction being otherwise similar to that shown in Fig. 1.

The copper of the layer 3 is preferably united to the top surface of the iron head wall l by the method disclosed and claimed in my copending application filed Dec. 11, 1942, Serial No. 468,623, as a result of the method there disclosed filament-like portions 8 integral with the body of the copper of layer 3 extend for a substantial distance into the pores of the iron head l thereby effecting a strong bonding contact between the layer of copper and the iron head and also facilitating rapid transfer of heat from the copper layer to the iron head. The layers of copper 3' and 3" in the modifications shown in Figs. 3 and 4 respectively are also united to the head wall of the piston as is the layer 3 above described.

portion 5 .to the periphery of the piston. Likewise in the modification shown in Fig. 4 the layer 3" increases in thickness from the projecting portion 5 of the head wall I" to the perlphery of the piston. But in the modification of 'Fig. 3 wherethe central projecting portion 5 is omitted from the head wall I' and the layer 3' of copper extends completely across the piston, the copper increases in thickness from the center of the combustion surface to the periphery of the piston. The highest temperature of a combustion surface is at its center because it is farthest from the cylinder walls and more or less in contact with the hottest gases of the explosion. By providing gradually increasing sections of copper from the central portion of the piston to the circumference of the same to carry off the increasing quantities of heat absorbed from the hot gases as the radius increases the temperature at the center of the combustion surface is materially lowered. Increasing the section thickness of the copper on an angle of between one-half and three degrees to the horizontal or preferably between one and three degrees to the horizontal has resulted in substantial reductions in surface temperatures over the entire top of the piston and the power of the engine has been stepped up by using a higher compression ratio and a more favorable spark advance for the ignition. The top surface of the iron head wall in each of the embodiments of the invention is machined or otherwise formed so as to incline downwardly toward the periphery thereof thereby permitting the topsurface of copperto lie in a horizontal plane and the copper to gradually increase in thickness towards the periphery of the piston.

The top surface of the iron head wall I of the piston has machined or otherwise formed therein a series of concentric grooves 9 for the reception of a corresponding series of projecting portions III on the lower surface of the layer of copper 3. By uniting the layer of copper 3 to the head portion I, by heating the copper in contact with the iron head portion at a temperature above the melting point of copper as disclosed in the above mentioned copending application, the molten copper readily flows into and fills the grooves 9 and also permeates the pores of the highly heated iron surrounding said grooves, and thereby also causing grooves 9 and projecting portions ill to be correspondingly shaped so that each projecting portion of copper snugly fits a groove in the iron. The grooves 9 may be of any suitable dimensions and spaced any suitable distance apart, as for instance approximately one-eighth of an inch wide by/ one-hundredth of an inch deep and one-fourth of an inch apart. This serrated construction resists any shearing stresses at the bonded surfaces of the iron and copper due to unequal degrees of expansion and contraction of the iron and copper resulting from changes in temperature. When expansion or contraction occurs the serrations act like anchor abutments resisting lateral displacement of the adjacent-surfaces of iron and copper. In the modi- I fled form of piston illustrated in Fig. 3 the head .wall I and the layer of copper 3are similarly provided with interfitting grooves; 9 and projecting portions [0 respectively. But in the modification shown in Fig. 4 the contacting surfaces of the 'ironhead l" and the layer of copper 3" are smooth, the serrated structure of the two embodiments previously described and shown in Figs. 1, 2 and 3 having been omitted.

The layer of copper 3 in the embodiment of the invention shown in Fig. 1 as well as the layer of copper in the two modifications shown in Figs. 3 and 4 has its peripheral edge chamfered at H, said chamfer starting from the peripheral line joining the layer of copper and iron head portion and extending inwardly and upwardly making an angle of approximately 20 to the vertical. Since the expansion of copper is considerably more than that of iron this chamfering prevents the copper expanding outwardly beyond the periphery of the iron head and dragging against the cylinder walls causing unnecessary wear and increasing the friction load of this piston in the cylinder.

As heretofore described reference has been made to the body of the piston including head and skirt portions as being composed of iron but any other suitable ferrous metal may be substituted therefor, likewise any suitable metal having thermal conductivity relatively large compared to that of iron may be substituted for the copper. v

I have illustrated and described my invention in embodiments which I have found very practical. I have not attempted to illustrate or describe other embodiments or adaptations as it is believed this disclosure will enable those skilled in the art to embody or adapt my invention as may be desired.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. A piston for internal combustion engines comprising an iron head wall and a skirt portion integral therewith, a layer of copper bonded to the top surface of said head wall, said layer of copper being of substantial thickness and covering substantially the entire top surface of said head wall, said layer of copper increasing in thickness from approximately the center-to the periphery of the piston to facilitate rapid transfer of increasing quantities of heat tothe ring belt section of the piston, the bonding surfaces of said layer of copper and said iron head wall being serrated to resist lateral displacement of said bonding surfaces, said layer of copper being cham ered inwardly from the. peripheral edge of said iron head wall to prevent the layer of copper dragging on the cylinder walls due to greater expansion of the copper layer.

2. A piston for internal combustion engines comprising an iron head wall and an iron skirt portion cast integrally with said head wall, said iron head wall having a central, circular raised portion, the top surface of said head wall being inclined downwardly from said central raised portion to the periphery of the piston, the inclined top surface of said head wall having a series of concentric grooves surrounding said central raised portion, a layer of copper of substantial thickness bonded to the inclined top surface from said central raised portion to the periphery of the piston, and having integral projecting portions filling said grooves, said layer of copper having its peripheral edge, chamfered to prevent said edge dragging against the cylinder walls.

3. A piston for internal combustion engines comprising an iron'head portion and a skirt portion integraltherewith, a layer of copper of substantial thickness covering substantially the entire'area of the top surface of said head portion, said layer of copper increasing in thickness toward the periphery of the piston to facilitate rapid transfer of increasing quantities of heat from the combustion surface of the piston to the ring -belt section thereof, the contacting surfaces of said heat portion and said layer of copper being circularly serrated to prevent lateral displacement of said contacting surfaces due to the greater expansion of the copper layer.

4. A piston for internal combustion engines comprising an. iron head portion and a layer of copper covering substantially the entire area of the top surface of said head portion and bonded thereto, said layer of copper increasing in thickness from its central portion'outwardly to facilitate rapid transfer of increasing quantities of heat from the combustion surface of the piston to the ring belt section thereof.

5. A piston for internal combustion engines comprising an iron body portion including head and skirt portions cast integrally, said head porv 3 tion having a central integral raised portion, a

layer of copper surrounding said central raised portion and covering substantially the entire area of said head portion from said central head portion to the periphery of the piston.

6.'A piston comprising a head wall of iron having a central raised pgrtion on-its top surface, a layer of copper surrounding said raised portion and covering said top surface from said central raised portion to the periphery of the piston, said layer of copper uniformally increasing in thickness from said central raised portion to the periphery of the piston.

7. In a piston, a ferrous metal head wall, a layer of non-ferrous metal of relatively high thermal conductivity compared to the ferrous metal and covering substantially the entire top surface of said head wall, said layer of non-ferrous metal increasing in thickness towards the periphery of the piston.

ravma E. ASKE. Y I 

